Deoxygenated blood returns to the heart through the venous system through the right atrium into the right ventricle. The right ventricle then pumps the blood into the lungs to be oxygenated and to the left atrium, then on to the left ventricle. The left ventricle supplies most of the heart's pumping power and pumps the oxygenated blood into systematic circulation.
When the right ventricle fails and does not adequately pump blood into the lungs, the blood backs up in the body's venous system. This causes swelling or congestion in the legs and ankles and swelling within the abdomen such as the gastrointestinal tract and liver and leading to ascites. There are two types of left-sided heart failure, diastolic failure, and systolic failure. In diastolic failure, the left ventricle loses its ability to relax normally, as the heart can't properly fill with blood during the resting period between each beat.
In systolic heart failure, because the left ventricle doesn't squeeze forcefully enough during systole, the heart doesn't pump blood out to the body as well as normal, which leads to a decrease in blood supply to organs, such as the kidneys, leading to organ failure. At the same time, the pressure in the veins of the lung increases, which may cause fluid accumulation in the lungs. This results in shortness of breath and pulmonary edema.
Despite maximal medical therapy, in the majority of patients with right ventricular or systolic left ventricular heart failure there is progressive pathological remodeling of the ventricles and pump failure and, over time, the heart can no longer keep up with the normal demands placed on it to pump blood to the rest of the body. Currently, as these patients progress towards advanced heart failure, the only treatment options are the major surgical procedures such as heart transplant and implantation of mechanical heart pumps, such as ventricular assist devices. One of the major limitations of ventricular assist devices are the need for major surgical procedures and the associated morbidity and costs. Due to complexity of the technology of the ventricular assist devices, there is high incidence of clot formation, damage to blood cells and device failure. Moreover, because of the large power requirement to drive the mechanical pump in the ventricular assist device, there is a need for an external drive line for an external power source, which leads to infections and poor quality of life.